Definition

A fluid-filled sac that forms in the breast that is sometimes filled with a mix of fluid and solid material. Breast cysts may occur in one or both breasts, and there may be more than one. Most cysts feel like a round or oval lump with a smooth, well-defined border that moves easily under the skin of the breast. But some cysts are too small to be felt. Symptoms may include pain or tenderness in the breast, especially around the time of a menstrual period, or a clear or cloudy fluid discharge from the nipple. Most breast cysts are not cancer and do not increase the risk of breast cancer. They can occur at any age but are most common in premenopausal women and in women taking hormone therapy for menopause.